With his inevitable nomination in jeopardy, Romney tore into his opponent relentlessly, dragging Santorum into a series of bloody sparring matches over the former Pennsylvania Senator's fiscal record. Santorum made an effort to fight back, but in the end he couldn't stop Romney from dismantling his staunch conservative record and redefining him as a Big Spending Washington RINO With Loose Principles.

As with previous debates, Romney's performance last night was actually pretty unremarkable. Yet one-by-one, he has managed to take out every candidate who has posed a threat to his frontrunner status.

So how does he do it?

The secret is great offense. Romney hones in like a laser to exploit potential weaknesses in his opponents' records, regardless of how trivial or irrelevant the issues might be to the race. By forcing his more-conservative rivals to defend their credibility, Romney has been able to fend off any real scrutiny or attacks on his own lukewarm conservative record.

Last night's Santorum smackdown was a great example of how this Jedi mind trick works. Romney's two fiercest attacks — over Santorum's support for earmarks and his 2004 endorsement of former Sen. Arlen Specter — are completely inconsequential to the race and to the question of whether or not Santorum is a "true" conservative.

Earmarks are a purely symbolic issue. They don't add to the federal debt, and no Republican Congress is going to lift the earmark ban anyway. But as long as Congress gets to decide where federal money gets spent, "earmarks" will exist, regardless of what they are called.

The Specter endorsement is even more irrelevant. In the debate, Romney used Santorum's 2004 decision to endorse his Pennsylvania Senate colleague over conservative darling Pat Toomey to argue that Santorum is quick to abandon his principles for political gain. But one unfortunate endorsement is hardly a smoking gun. Romney's suggestion that Santorum's endorsement was responsible for Specter's 2004 win, therefore he is also responsible for Specter's decisive 2008 Obamacare vote is completely ludicrous.

That didn't stop the attacks from working. Romney managed to drag Santorum into a rambling discussion on earmarks, forcing him to defend the practive — and, by extension, defend government waste. Later, he backed Santorum so far into a corner on the Specter issue that Santorum actually started apologizing for his less-than-conservative indiscretions. Meanwhile, Romney was able to deflect any counterattacks against his own politically expedient compromises.

Romney even managed to turn the tables on the contraception issue, drilling down on Santorum's vote for Title X, which provides funding for Planned Parenthood. Santorum was so busy deflecting the attacks, he forgot to mention that Romney was pro-choice until about 2005.

This is the same strategy Romney has used to inoculate other Republican opponents who have posed a threat to his presumptive nomination. Romney effectively ended Rick Perry's bid by turning the gun-wielding Texas cowboy into a bleeding-heart, immigrant-loving liberal who wants to infringe on parental rights.

In reality, all of the other 2012 candidates are more conservative than Romney, and all of them have a more natural affinity with Republican primary voters. Romney's flipflopping record and general unrelatability make it impossible to compete on ideological purity or emotional appeal. But rather than try to keep up, Romney seems determined to bend the GOP to his will. As long as his opponents keep caving, this "if you can't join 'em, beat 'em" plan looks like it might work.